1. Technical Field
The present invention relates generally to techniques for selectively storing content in a compressed form in a content delivery network edge server cache and for serving the content to an end user browser.
2. Description of the Related Art
A content delivery network (“CDN”) is a collection of content servers and associated control mechanisms that offload work from Web site origin servers by delivering content on their behalf to end users. A well-managed CDN achieves this goal by serving some or all of the contents of a site's Web pages, thereby reducing the customer's costs while enhancing an end user's browsing experience from the site. In operation, the CDN uses a request routing mechanism to locate a CDN content server close to the client to serve each request directed to the CDN, where the notion of “close” is based, in part, on evaluating results of network traffic tests.
Data compression techniques are well-known in the art. In HTTP 1.1, a Web server may compress an object, e.g., the HTML comprising a base page, to reduce the download time of the page from the server to a requesting end user browser. Most browsers in use today are capable of receiving compressed content and decompressing such content for display. A recent study showed that over 95% of users have browsers capable of decoding compressed HTMLs. A browser indicates to a Web server that it can receive compressed content in the HTTP request header. The Web server may send compressed content, indicating in the HTTP response header that the object was compressed and should be uncompressed before rendering. Servers should not send compressed HTMLs to browsers that do not include decompression capability in the request header. The benefits of compressing data in a typical HTTP 1.1 client-server session is described in a W3C Note titled Network Performance Effects of HTTP/1.1, CSS1, and PNG, by Neilsen et al., June 1997.
While browsers have had the capability to decompress content for years, most servers do not for various reasons, primarily due to issues involving compatibility, processor workload and complexity of content management.
While content delivery network service providers (CDNSPs) have developed and implemented techniques for accelerating delivery of content between origin server sites and the CDN edge servers, delivery over the so-called “last mile” (from the ISP at which the edge server is located to the end user) has not been adequately addressed.
It would be highly desirable to accelerate the delivery of content between a CDN edge server and the requesting end user browser through selective delivery of compressed content.